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User profile for user: LightningMike
LightningMike Author
User level: Level 1
41 points

REINSTALL MOJAVE on iMac currently running Catalina

My 2019 iMac27 Retina 250 SSD was shipped with Mojave v.10.12.4 and I really want to go back to that macOS and not use Catalina. I have tried various methods, including creating a USB installer stick and in that case, it seemed like its running fine...


To continue we need to erase the volume at /Volumes/USB.

If you wish to continue type (Y) then press return: y

Erasing disk: 0%... 10%... 20%... 30%... 100%

Copying to disk: 0%... 100%

IA app name cookie write failed

The copy of the installer app failed.


What would cause the installer App to fail?


So I tried doing the Internet Recovery; Boot holding CMD+Option+R and the process seems to start, I got to the spinning globe... but then a screen pops up with a few choices including Restore from Time Machine, Reinstall MacOS, Get Help Online, and Disk Utility. , but when I went to the selection where you have options to reinstall the OS, a popup appeared saying it was going to reinstall Catalina.


I am fully backed up as far as my HDD goes, not worried about Apps I can reinstall, so are there any other options? Is there a way to check the USB installer to make sure its exactly right? Does using the BT keyboard and mouse have any effect on things when you are running from terminal?

iMac 27″ 5K, macOS 10.15

Posted on May 28, 2020 9:31 AM

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User profile for user: babowa
babowa
User level: Level 9
78,405 points

Posted on May 29, 2020 4:24 PM

So I tried doing the Internet Recovery; Boot holding CMD+Option+R and the process seems to start, I got to the spinning globe... but then a screen pops up with a few choices including Restore from Time Machine, Reinstall MacOS, Get Help Online, and Disk Utility. , but when I went to the selection where you have options to reinstall the OS, a popup

appeared saying it was going to reinstall Catalina.


Did you go to Disk utility and erase your drive first?


If you want to install an older OS than what is currently running, you absolutely need to erase the hard drive first. When that is finished, try the reinstall option again. If you used the correct key combo when booting up, it should offer the OS it came with.

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User profile for user: babowa
babowa
User level: Level 9
78,405 points

May 29, 2020 4:24 PM in response to LightningMike

So I tried doing the Internet Recovery; Boot holding CMD+Option+R and the process seems to start, I got to the spinning globe... but then a screen pops up with a few choices including Restore from Time Machine, Reinstall MacOS, Get Help Online, and Disk Utility. , but when I went to the selection where you have options to reinstall the OS, a popup

appeared saying it was going to reinstall Catalina.


Did you go to Disk utility and erase your drive first?


If you want to install an older OS than what is currently running, you absolutely need to erase the hard drive first. When that is finished, try the reinstall option again. If you used the correct key combo when booting up, it should offer the OS it came with.

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User profile for user: Barney-15E
Barney-15E
User level: Level 10
116,110 points

May 28, 2020 10:23 AM in response to LightningMike

Is the USB stick directly attached to the iMac USB port or in a Hub? I've found it must be directly connect for both the creating and for the install.


From Internet Recovery, you would want to use cmd-shift-Opt-R to install the OS that shipped on your Mac.

If that still wants to reinstall Recovery, you might need to erase the entire drive in Disk Utility.

In Disk Utility, select Show all Devices from the View button popup menu.

The, select the device and erase that using Mac OS Extended (Journaled). Mojave should convert it to APFS, but some people have noted that the Mojave installer didn't like seeing APFS to start with. Not sure if that has been resolved.

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User profile for user: LightningMike
LightningMike Author
User level: Level 1
41 points

May 28, 2020 7:57 PM in response to Barney-15E

Hi Barney... Your suggestion about the port was right. The USB was in a remote port. I shut down, pulled the USB and plugged it in the back of the mac. Restarted the process, and within 30 seconds the progress bar had reached the same marked with painters tape spot and its seemed to stall again. The little gear under the apple logo is not moving.


I know this process can take some time, and I did use a brand new Sandisk Extreme Pro 3.1 128GB so space and speed shouldn't be a big issue. I'll give it an hour or so and will let you know if anything's changed. I'm all backed up, I don't care if I have to erase the HDD, there's nothing important on it. I just want to get rid of Catalina and back to Mojave. Whatever method works isn't an issue, but I want to make sure it's secure and legit.


Thank you for taking to time to offer some advice.


Mike

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User profile for user: LightningMike
LightningMike Author
User level: Level 1
41 points

May 29, 2020 1:21 PM in response to Barney-15E

Never finished after several hours and 2-3 tries. I never see the installer page with any kind of menu, its just a black screen, Apple logo, a small turning gear under it, and a slit-like progress bar that is similar to a cold boot. Gets about 30% across every time in 30 seconds and stops there. The black screen with the white apple and gear remains frozen.

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REINSTALL MOJAVE on iMac currently running Catalina

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